1. Field of the Invention
The present invention relates to a ball grid array (hereinafter referred to as "BGA") package, and more particularly, to a semiconductor device for a memory module for high density mounting by forming through holes in the upper portion of a semiconductor substrate and forming solder balls on the lower portion of the semiconductor substrate. A method for manufacturing the semiconductor device is also provided.
2. Description of Related Art
The desire for high performance and multifunction in electronic apparatuses has been heightened along with the continuing trend towards smaller and thinner dimensions. Various semiconductor device mounting methods are in demand for efficiently mounting large capacity memory devices within a limited internal space.
As one method for achieving the above objectives, an Over Molded Pad Array Carrier (OMPAC) package of Motorola is disclosed in ASIC & EDA, pp. 9-15, March 1993, and may be taken as an example.
FIG. 1 is a vertical sectional view showing an example of the conventional semiconductor device.
Referring to FIG. 1, the semiconductor device includes a sub-substrate 11 having through holes 15 spaced by a predetermined interval, and conductive contact pads 13 formed on predetermined regions of the sub-substrate 11. Additionally, a semiconductor chip 12 is mounted on the subsubstrate 11 by means of an insulating adhesive, for example. A wire 14 electrically connects a bonding pad of the semiconductor chip 12 to the conductive contact pad 13, and the wires 14 and the semiconductor chip 12 are molded with epoxy molding compound (hereinafter referred to as "EMC") to form a package body 10. Solder bump electrodes, (i.e., solder balls 16), are provided on the lower portion of the through holes 15 in the sub-substrate 11, and a plurality of electrode pads 18 are mounded onto a main substrate 17 to correspond to the solder bump electrodes 16.
After electrical connection through the wire 14 (made from gold (Au), for example), is finished by mounting the semiconductor chip 12 onto the sub-substrate 11, a transfer molding is performed by means of EMC. The solder balls 16 are formed on a lower surface of the sub-substrate 11 having to correspond to the through holes 15, thereby obtaining the semiconductor device having solder bump electrodes 16 via a reflow soldering. This is the BGA package.
The BGA package constructed as above is mounted onto the main substrate 17, and the solder bump electrodes are electrically connected to respective electrode pads 18 on the main substrate 17 via reflow soldering, so that the assembly of the semiconductor device is completed.
The BGA package reduces the mounting area on the main substrate by approximately 30% compared with a quad flat package (QFP) which has the same pin count, but the BGA package described here is limited to mounting two-dimensional structures in which all connection terminals between the main substrate and package are positioned in the same plane.
Moreover, in the conventional BGA package, a resin encapsulation portion for protecting the semiconductor chip 12 from surrounding environment is formed on only one side at the interface of the package body 10 and subsubstrate 11. Also, the solder bump electrodes 16 formed under the sub-substrate 11 are reflow-soldered to the electrode pads 18 and have relatively weak structure. They are thus exposed to the external environment. Therefore, the internal and external environmental characteristics of the BGA package are resulting in worse than those of other packages in general use, thereby degraded performance thereof.